Verifying proper operation of the instruction execution protection architecture

ABSTRACT

A computer-implemented method includes executing one or more tests on a computing device. The computing device has Instruction Execution Protection (IEP), and each test of the one or more tests includes selectively setting one or more IEP bits of one or more page tables, where each IEP bit prevents code in a respective storage block from being executed. During the one or more tests, an IEP exception is detected, by a computer processor, each time an attempt is made to execute code in a storage block for which a respective IEP bit is set. Test results of the one or more tests are determined based on the detecting. A remedial action is performed in response to the test results of the one or more tests.

BACKGROUND

Embodiments of the present invention relate to system testing and, morespecifically, to verifying proper operation of the Instruction ExecutionProtection (IEP) architecture.

Main memory includes both instructions and data. Generally, execution ofdata should be avoided, as such execution can lead to unexpected resultsgiven that data is not meant to be treated as instructions. However, amalicious program may attempt to execute data in memory specifically toharm to the computer system.

IEP is an architecture introduced with zMidas processors of the zSystem® by International Business Machines®. IEP is designed to preventdata portions of memory from being executed. Specifically, IEPassociates a bit with each page table. Page tables provide mappingsbetween virtual addresses and physical addresses in main memory. Whenthe IEP bit of a page table is set, execution of information stored in avirtual address can be prevented, as such execution requires translationthrough the applicable page table.

SUMMARY

According to an embodiment of the present invention, acomputer-implemented method includes executing one or more tests on acomputing device. The computing device has Instruction ExecutionProtection (IEP), and each test of the one or more tests includesselectively setting one or more IEP bits of one or more page tables,where each IEP bit prevents code in a respective storage block frombeing executed. During the one or more tests, an IEP exception isdetected, by a computer processor, each time an attempt is made toexecute code in a storage block for which a respective IEP bit is set.Test results of the one or more tests are determined based on thedetecting. A remedial action is performed in response to the testresults of the one or more tests.

In another embodiment, a system includes a memory havingcomputer-readable instructions and one or more processors for executingthe computer-readable instructions. The computer-readable instructionsinclude executing one or more tests on a computing device. The computingdevice has IEP, and each test of the one or more tests includesselectively setting one or more IEP bits of one or more page tables,where each IEP bit prevents code in a respective storage block frombeing executed. Further according to the computer-readable instructions,during the one or more tests, an IEP exception is detected each time anattempt is made to execute code in a storage block for which arespective IEP bit is set. Test results of the one or more tests aredetermined based on the detecting. A remedial action is performed inresponse to the test results of the one or more tests.

In yet another embodiment, a computer-program product for testingfunctionality of IEP includes a computer-readable storage medium havingprogram instructions embodied therewith. The program instructions areexecutable by a processor to cause the processor to perform a method.The method includes executing one or more tests on a computing device.The computing device has IEP, and each test of the one or more testsincludes selectively setting one or more IEP bits of one or more pagetables, where each IEP bit prevents code in a respective storage blockfrom being executed. Further according to the method, during the one ormore tests, an IEP exception is detected each time an attempt is made toexecute code in a storage block for which a respective IEP bit is set.Test results of the one or more tests are determined based on thedetecting. A remedial action is performed in response to the testresults of the one or more tests.

Additional features and advantages are realized through the techniquesof the present invention. Other embodiments and aspects of the inventionare described in detail herein and are considered a part of the claimedinvention. For a better understanding of the invention with theadvantages and the features, refer to the description and to thedrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter regarded as the invention is particularly pointed outand distinctly claimed in the claims at the conclusion of thespecification. The foregoing and other features and advantages of theinvention are apparent from the following detailed description taken inconjunction with the accompanying drawings in which:

FIG. 1 is a diagram of a test system for verifying the functionality ofInstruction Execution Protection (IEP) on a computing device, accordingto some embodiments of this invention;

FIG. 2 is a block diagram of a first test of the functionality of IEP,within a uniprocessor system, according to some embodiments of thisinvention;

FIG. 3 is a block diagram of a second test of the functionality of IEP,within a multiprocessor system, according to some embodiments of thisinvention;

FIG. 4 is a block diagram of a third test of the functionality of IEP,within a multiprocessor system, according to some embodiments of thisinvention;

FIG. 5 is a block diagram of a fourth test of the functionality of IEP,within a multiprocessor system, according to some embodiments of thisinvention;

FIG. 6 is a block diagram of a fifth test of the functionality of IEP,within a multiprocessor system, according to some embodiments of thisinvention;

FIG. 7 is a block diagram of a sixth test of the functionality of IEP,within a multiprocessor system, according to some embodiments of thisinvention;

FIG. 8 is a flow diagram of a method for testing the functionality ofIEP, according to some embodiments of this invention; and

FIG. 9 is a block diagram of a computer system for implementing some orall aspects of the test system, according to some embodiments of thisinvention.

DETAILED DESCRIPTION

To ensure that data portions of memory are not executed, it is criticalto ensure that Instruction Execution Protection (IEP) is operating asexpected on each computing device onto which it is incorporated. Giventhat IEP is a relatively new technology, there is no conventionalmechanism for testing IEP to ensure it operates properly.

Turning now to an overview of aspects of the present invention, someembodiments of a test system verify the functionality of an IEParchitecture. Specifically, the test system may verify properfunctionality in a uniprocessor environment, a multiprocessorenvironment, or both. Further, in some embodiments, the test system mayoperate in a virtual machine, such as by creating a controlled logicalpartition in which the test system runs.

FIG. 1 is a diagram of the test system 100 for verifying thefunctionality of IEP on a computing device 150, according to someembodiments of this invention. More specifically, the test system 100may selectively set IEP bits 160 of the page tables 170 used totranslate between virtual memory 180 and physical memory in thecomputing device 150, and may then determine whether IEP exceptionsoccur as expected. In some embodiments, the test system 100 may accessone or more virtual machines 155 of the computing device 150, to verifythat IEP is operating properly within those virtual machines 155. Insome embodiments, the test system 100 may be able to test thefunctionality of IEP on a uniprocessor system, a multiprocessor system,or both. If one or more virtual machines 155 are being tested, thevirtual machines 155 need not have the same processor architecture asone another, and need not have the same processor architecture of thephysical computing device 150. Thus, the test system 100 may, in somecases, test the functionality of both uniprocessor and multiprocessorsystems on the computing device 150.

The test system 100 may perform one or more tests on the computingdevice 150 to determine whether IEP is operating properly. Each testperformed may have expected results that can be verified through anexamination of the memory upon which processors involved are operating.Specifically, for instance, whenever an attempt is made to executeinformation in a storage block protected by IEP (i.e., corresponding toa page table 170 with a set IEP bit), an IEP exception may occur, andthe test system 100 may detect these exceptions as the test results.Thus, the test system 100 may determine whether these exceptions occurat expected points during the tests. It will be understood that othermechanisms exist and can be used for verifying that the tests perform asexpected.

Several tests are described below as usable by the test system 100. Itwill be understood that one or more of these tests may be run by thetest system 100 on the computing device 150, and it need not be the casethat every such test is run on the computing device 150. Further, itwill be understood that one or more other tests may be run by the testsystem 100 as an alternative to, or in addition to, those describedherein.

FIG. 2 is a block diagram of a first test 200 of the functionality ofIEP, within a uniprocessor system, according to some embodiments of thisinvention. In the first test 200, the test system 100 may instruct auniprocessor 210 to selectively set the IEP bit 160 of one or more pagetables 170, while leaving the IEP bit 160 unset for one or more otherpage tables 170. In the first test 200, the test system 100 may providea stream of instructions that include instructions to branch to one ormore virtual memory addresses. The one or more virtual memory addressesmay reside within a set of one or more storage blocks 230, with eachvirtual memory address residing in a corresponding storage block 230.Each storage block 230 may be associated with a page table 170, whichmay or may not have a set IEP bit 160. If the IEP bit 160 associatedwith the storage block 230 is set, then that storage block 230 may bedeemed protected. Assuming IEP is operating correctly, in someembodiments, upon branching to a protected storage block 230, theuniprocessor 210 is unable to execute the information stored in thestorage block 230, but upon branching to an unprotected storage block230, the uniprocessor is able to execute the information stored in thestorage block 230. Additionally, in some cases, the first test 200 mayexecute instructions that walk into a protected storage block 230 froman unprotected storage block 230, upon crossing a page boundary. Inthose cases, in some embodiments, the expected behavior is for theuniprocessor 210 to be able to execute the information stored in theunprotected storage block 230 but not in the protected storage block230. The test system 100 may verify that this proper operation of IEPoccurs during the first test 200.

FIG. 3 is a block diagram of a second test 300 of the functionality ofIEP, within a multiprocessor system, according to some embodiments ofthis invention. As shown in FIG. 3, a multiprocessor system may includea master processor 310 and one or more slave processors 320. In thesecond test 300, the master processor 310 and the slave processors 320may all operate on common storage 330, which may be virtual. As part ofthe second test 300, the test system 100 may provide the masterprocessor 310 with an instruction stream that causes the masterprocessor to set the IEP bit 160 of one or more page tables 170, whileleaving the IEP bit 160 unset for one or more other page tables 170. Inthe second test 300, both the master processor 310 and the slaveprocessors 320 may execute a stream of instructions, includinginstructions to execute code in protected storage of the common storage330. The test system 100 may confirm that the master processor 310 andthe slave processors 320 are able to execute code in the unprotectedstorage of the common storage 330, but are unable to execute code in theprotected storage of the common storage 330.

FIG. 4 is a diagram of a third test 400 of the functionality of IEP,again within a multiprocessor system, according to some embodiments ofthis invention. As shown, in this third test 400, the master processor310 and a first set of slave processors 320 may operate on a firststorage 410 in virtual memory, while a second set of slave processors320 may operate on a second storage 420 of virtual memory, which differsfrom the first storage 410. As with the previous test on amultiprocessor system, the master processor 310 may be instructed to setthe IEP bit 160 for one or more page tables 170, thus protecting thecorresponding storage blocks, while leaving the IEP bit 160 unset on oneor more other page tables 170. However, because the master processor 310operates on the first storage 410 and not on the second storage 420, insome embodiments, the expected behavior is for the second set of slaveprocessors 320 operating on the second storage 420 to be able to executeinformation from each storage block encountered. In contrast, in someembodiments, the master processor 310 and the first set of slaveprocessors 320 operating on the first storage 410 are expected to beable to execute information in unprotected storage blocks but not inprotected storage blocks. The test system 100 may verify that this iswhat occurs during the third test 400.

FIG. 5 is a diagram of a fourth test 500 of the functionality of IEP,again within a multiprocessor system, according to some embodiments. Inthis fourth test 500, the master processor 310 may operate on the firststorage 410 of virtual memory, while one or more slave processors 320operate on the second storage 420 of virtual memory, which may bedistinct from the first storage 410. However, the master processor 310may set the IEP bit 160 of one or more page tables 170 of the secondstorage 420, while leaving one or more other IEP bits 160 unset in thesecond storage 420. In some embodiments, the master processor 310 doesnot set any IEP bits 160 in the first storage 410. According to someembodiments, the expected behavior is for the slave processors 320 to beable to execute code in unprotected storage blocks while being unable toexecuted code in protected storage blocks. The master processor 310 maybe expected to be able to execute all code it is instructed to execute,as in some embodiments, the master processor 310 is not expected toencounter a protected storage block. The test system 100 may verify thatthis occurs during execution of the fourth test 500.

FIG. 6 is a diagram of a fifth test 600 of the functionality of IEP,again within a multiprocessor system, according to some embodiments. Inthis fifth test 600, the master processor 310 may operate on a firststorage 410 in virtual memory, while a first set of slave processors 320operate on a second storage 420 that is in virtual memory and distinctfrom the first storage 410, and while a second set of the slaveprocessors 320 operate on a third storage 630 that is in virtual memoryand distinct from the first storage 410 and the second storage 420. Themaster processor 310 may set the IEP bit 160 of one or more page tables170 of the second storage 420, while leaving one or more other IEP bits160 unset in the second storage 420. In some embodiments, the masterprocessor 310 does not set any IEP bits 160 in the first storage 410 orthe third storage 630. According to some embodiments, the expectedbehavior is for the first set of slave processors 320 to be able toexecute code in unprotected storage blocks while being unable toexecuted code in protected storage blocks. The master processor 310 andthe second set of slave processors 320 may be expected to be able toexecute all code they are instructed to execute, as in some embodiments,they are not expected to encounter a protected storage block. The testsystem 100 may verify that this occurs during the fifth test 600.

FIG. 7 is a diagram of a sixth test 700 of the functionality of IEP,again within a multiprocessor system, according to some embodiments. Inthis sixth test 700, the master processor 310 may operate on a firststorage 410 in virtual memory, while one or more slave processors 320operate on a second storage 420 in virtual memory, where the secondstorage 420 is distinct from the first storage 410. The master processor310 may set the IEP bit 160 of one or more page tables 170 of the firststorage 410 on which it operates, while leaving one or more other IEPbits 160 unset in the first storage 410. In some embodiments, the masterprocessor 310 does not set any IEP bits 160 in the second storage 420.According to some embodiments, the expected behavior is for the slaveprocessors 320 to encounter only unprotected storage and to be able toexecute any code they are instructed to execute. In contrast, in someembodiments, the master processor 310 is able to execute code inunprotected storage blocks while being unable to execute code inprotected storage blocks. The test system 100 may verify that thisoccurs in the sixth test 700.

Regardless of the specific tests performed, the test system 100 maydetermine whether IEP operates correctly based on whether the results ofthe tests are as expected. The tests may indicate, for example, whetherand where IEP exceptions occurred or whether and where certain code wasexecuted inside and outside protected storage. The results of the testsmay be determined based on these indications and, further, may indicatewhether IEP operates correctly and, if not, in what way IEP is operatingincorrectly. After performing one or more tests, the test system 100 mayautomatically perform a remedial action in response to the results ofthose tests. In some embodiments, the remedial action may includereporting the results of the tests, thus enabling manual or automatichandling of the results.

FIG. 8 is a flow diagram of a method 800 for testing IEP functionalityon a computing device 150, according to some embodiments of thisinvention. As shown in FIG. 8, at block 805, the test system 100 may beloaded onto a computing device 150 having IEP. In some embodiments, thecomputing device 150 may be a new computer system, and the test system100 may be used to verify operation of IEP on the computing device 150before the computing device 150 is sold or otherwise released for use.At block 810, the test system 100 may be initiated on the computingdevice 150.

At decision block 815, the test system 100 may determine whether anytests not yet run are available to be run on the computing device 150.In some embodiments, this determination may be performed automaticallyby the test system 100, such as by determining whether any testsapplicable to the computing device 150 have not yet been run on thecomputing device 150. If the computing device 150 or, if applicable, thevirtual machine 155 on which the test system 100 was initiated is auniprocessor system, then the test system 100 may seek a test designedfor testing IEP on a uniprocessor system. If the computing device 150or, if applicable, the virtual machine 155 on which the test system 100was initiated is a multiprocessor system, then the test system 100 mayseek a test designed for testing IEP on a multiprocessor system.However, if the computing device 150 includes both at least oneuniprocessor system and at least one multiprocessor system, then testsfor both uniprocessor and multiprocessor systems may be run on thecomputing device 150. In some embodiments, a user may manually determinewhether a test not yet run is available to be run at decision block 815,and the test system's determination may thus be based on user entry.

If no tests remain to be run at decision block 815, then the method 800may end at block 820 by automatically performing a remedial action onthe computing device 150 in response to the results of the tests. Insome embodiments, this remedial action may include reporting negativeresults of any tests run.

If a test is identified at decision block 815 as applicable and not yethaving been run, then at block 825, the test system 100 may run thattest. For example, and not by way of limitation, the test may be one ofthose described above. At block 830, after running the test, the testsystem 100 may verify proper operation of the test 110. In other words,the test system 100 may determine whether the test ran as expected. Insome embodiments, the test system 100 may be aware of the expectedresults and may thus perform this verification automatically.Alternatively, however, manual verification may be received by the testsystem 100. The method 800 may then return to decision block 815 todetermine whether additional tests remain to be run.

FIG. 9 illustrates a block diagram of a computer system 900 for use inimplementing a test system 100 or method according to some embodiments.The test systems 100 and methods described herein may be implemented inhardware, software (e.g., firmware), or a combination thereof. In someembodiments, the methods described may be implemented, at least in part,in hardware and may be part of the microprocessor of a special orgeneral-purpose computer system 900, such as a personal computer,workstation, minicomputer, or mainframe computer. For instance, thecomputing device 150 on which the test system 100 runs may be a computersystem 900 as illustrated in FIG. 9.

In some embodiments, as shown in FIG. 9, the computer system 900includes a processor 905, memory 910 coupled to a memory controller 915,and one or more input devices 945 and/or output devices 940, such asperipherals, that are communicatively coupled via a local I/O controller935. These devices 940 and 945 may include, for example, a printer, ascanner, a microphone, and the like. Input devices such as aconventional keyboard 950 and mouse 955 may be coupled to the I/Ocontroller 935. The I/O controller 935 may be, for example, one or morebuses or other wired or wireless connections, as are known in the art.The I/O controller 935 may have additional elements, which are omittedfor simplicity, such as controllers, buffers (caches), drivers,repeaters, and receivers, to enable communications.

The I/O devices 940, 945 may further include devices that communicateboth inputs and outputs, for instance disk and tape storage, a networkinterface card (MC) or modulator/demodulator (for accessing other files,devices, systems, or a network), a radio frequency (RF) or othertransceiver, a telephonic interface, a bridge, a router, and the like.

The processor 905 is a hardware device for executing hardwareinstructions or software, particularly those stored in memory 910. Theprocessor 905 may be a custom made or commercially available processor,a central processing unit (CPU), an auxiliary processor among severalprocessors associated with the computer system 900, a semiconductorbased microprocessor (in the form of a microchip or chip set), amacroprocessor, or other device for executing instructions. Theprocessor 905 includes a cache 970, which may include, but is notlimited to, an instruction cache to speed up executable instructionfetch, a data cache to speed up data fetch and store, and a translationlookaside buffer (TLB) used to speed up virtual-to-physical addresstranslation for both executable instructions and data. The cache 970 maybe organized as a hierarchy of more cache levels (L1, L2, etc.).

The memory 910 may include one or combinations of volatile memoryelements (e.g., random access memory, RAM, such as DRAM, SRAM, SDRAM,etc.) and nonvolatile memory elements (e.g., ROM, erasable programmableread only memory (EPROM), electronically erasable programmable read onlymemory (EEPROM), programmable read only memory (PROM), tape, compactdisc read only memory (CD-ROM), disk, diskette, cartridge, cassette orthe like, etc.). Moreover, the memory 910 may incorporate electronic,magnetic, optical, or other types of storage media. Note that the memory910 may have a distributed architecture, where various components aresituated remote from one another but may be accessed by the processor905.

The instructions in memory 910 may include one or more separateprograms, each of which comprises an ordered listing of executableinstructions for implementing logical functions. In the example of FIG.9, the instructions in the memory 910 include a suitable operatingsystem (OS) 911. The operating system 911 essentially may control theexecution of other computer programs and provides scheduling,input-output control, file and data management, memory management, andcommunication control and related services.

Additional data, including, for example, instructions for the processor905 or other retrievable information, may be stored in storage 920,which may be a storage device such as a hard disk drive or solid statedrive. The stored instructions in memory 910 or in storage 920 mayinclude those enabling the processor to execute one or more aspects ofthe test systems 100 and methods of this disclosure.

The computer system 900 may further include a display controller 925coupled to a display 930. In some embodiments, the computer system 900may further include a network interface 960 for coupling to a network965. The network 965 may be an IP-based network for communicationbetween the computer system 900 and an external server, client and thelike via a broadband connection. The network 965 transmits and receivesdata between the computer system 900 and external systems. In someembodiments, the network 965 may be a managed IP network administered bya service provider. The network 965 may be implemented in a wirelessfashion, e.g., using wireless protocols and technologies, such as WiFi,WiMax, etc. The network 965 may also be a packet-switched network suchas a local area network, wide area network, metropolitan area network,the Internet, or other similar type of network environment. The network965 may be a fixed wireless network, a wireless local area network(LAN), a wireless wide area network (WAN) a personal area network (PAN),a virtual private network (VPN), intranet or other suitable networksystem and may include equipment for receiving and transmitting signals.

Test systems 100 and methods according to this disclosure may beembodied, in whole or in part, in computer program products or incomputer systems 900, such as that illustrated in FIG. 9.

Technical effects and benefits of some embodiments include the abilityto test a computing device 150 to verify operation of IEP and, thus, todetermine whether the computing device 150 will operate as intended fora user. Specifically, the test system 100 may run various tests toensure that the IEP bit for storage blocks is respected in bothuniprocessor and multiprocessor systems, whether physical or virtual.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

The corresponding structures, materials, acts, and equivalents of allmeans or step plus function elements in the claims below are intended toinclude any structure, material, or act for performing the function incombination with other claimed elements as specifically claimed. Thedescription of the present invention has been presented for purposes ofillustration and description, but is not intended to be exhaustive orlimited to the invention in the form disclosed. Many modifications andvariations will be apparent to those of ordinary skill in the artwithout departing from the scope and spirit of the invention. Theembodiments were chosen and described in order to best explain theprinciples of the invention and the practical application, and to enableothers of ordinary skill in the art to understand the invention forvarious embodiments with various modifications as are suited to theparticular use contemplated.

The present invention may be a system, a method, and/or a computerprogram product at any possible technical detail level of integration.The computer program product may include a computer readable storagemedium (or media) having computer readable program instructions thereonfor causing a processor to carry out aspects of the present invention.

The computer readable storage medium can be a tangible device that canretain and store instructions for use by an instruction executiondevice. The computer readable storage medium may be, for example, but isnot limited to, an electronic storage device, a magnetic storage device,an optical storage device, an electromagnetic storage device, asemiconductor storage device, or any suitable combination of theforegoing. A non-exhaustive list of more specific examples of thecomputer readable storage medium includes the following: a portablecomputer diskette, a hard disk, a random access memory (RAM), aread-only memory (ROM), an erasable programmable read-only memory (EPROMor Flash memory), a static random access memory (SRAM), a portablecompact disc read-only memory (CD-ROM), a digital versatile disk (DVD),a memory stick, a floppy disk, a mechanically encoded device such aspunch-cards or raised structures in a groove having instructionsrecorded thereon, and any suitable combination of the foregoing. Acomputer readable storage medium, as used herein, is not to be construedas being transitory signals per se, such as radio waves or other freelypropagating electromagnetic waves, electromagnetic waves propagatingthrough a waveguide or other transmission media (e.g., light pulsespassing through a fiber-optic cable), or electrical signals transmittedthrough a wire.

Computer readable program instructions described herein can bedownloaded to respective computing/processing devices from a computerreadable storage medium or to an external computer or external storagedevice via a network, for example, the Internet, a local area network, awide area network and/or a wireless network. The network may comprisecopper transmission cables, optical transmission fibers, wirelesstransmission, routers, firewalls, switches, gateway computers and/oredge servers. A network adapter card or network interface in eachcomputing/processing device receives computer readable programinstructions from the network and forwards the computer readable programinstructions for storage in a computer readable storage medium withinthe respective computing/processing device.

Computer readable program instructions for carrying out operations ofthe present invention may be assembler instructions,instruction-set-architecture (ISA) instructions, machine instructions,machine dependent instructions, microcode, firmware instructions,state-setting data, configuration data for integrated circuitry, oreither source code or object code written in any combination of one ormore programming languages, including an object oriented programminglanguage such as Smalltalk, C++, or the like, and procedural programminglanguages, such as the “C” programming language or similar programminglanguages. The computer readable program instructions may executeentirely on the user's computer, partly on the user's computer, as astand-alone software package, partly on the user's computer and partlyon a remote computer or entirely on the remote computer or server. Inthe latter scenario, the remote computer may be connected to the user'scomputer through any type of network, including a local area network(LAN) or a wide area network (WAN), or the connection may be made to anexternal computer (for example, through the Internet using an InternetService Provider). In some embodiments, electronic circuitry including,for example, programmable logic circuitry, field-programmable gatearrays (FPGA), or programmable logic arrays (PLA) may execute thecomputer readable program instructions by utilizing state information ofthe computer readable program instructions to personalize the electroniccircuitry, in order to perform aspects of the present invention.

Aspects of the present invention are described herein with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems), and computer program products according to embodiments of theinvention. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer readable program instructions.

These computer readable program instructions may be provided to aprocessor of a general purpose computer, special purpose computer, orother programmable data processing apparatus to produce a machine, suchthat the instructions, which execute via the processor of the computeror other programmable data processing apparatus, create means forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks. These computer readable program instructionsmay also be stored in a computer readable storage medium that can directa computer, a programmable data processing apparatus, and/or otherdevices to function in a particular manner, such that the computerreadable storage medium having instructions stored therein comprises anarticle of manufacture including instructions which implement aspects ofthe function/act specified in the flowchart and/or block diagram blockor blocks.

The computer readable program instructions may also be loaded onto acomputer, other programmable data processing apparatus, or other deviceto cause a series of operational steps to be performed on the computer,other programmable apparatus or other device to produce a computerimplemented process, such that the instructions which execute on thecomputer, other programmable apparatus, or other device implement thefunctions/acts specified in the flowchart and/or block diagram block orblocks.

The flowchart and block diagrams in the Figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods, and computer program products according to variousembodiments of the present invention. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof instructions, which comprises one or more executable instructions forimplementing the specified logical function(s). In some alternativeimplementations, the functions noted in the blocks may occur out of theorder noted in the Figures. For example, two blocks shown in successionmay, in fact, be executed substantially concurrently, or the blocks maysometimes be executed in the reverse order, depending upon thefunctionality involved. It will also be noted that each block of theblock diagrams and/or flowchart illustration, and combinations of blocksin the block diagrams and/or flowchart illustration, can be implementedby special purpose hardware-based systems that perform the specifiedfunctions or acts or carry out combinations of special purpose hardwareand computer instructions.

The descriptions of the various embodiments of the present inventionhave been presented for purposes of illustration, but are not intendedto be exhaustive or limited to the embodiments disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the describedembodiments. The terminology used herein was chosen to best explain theprinciples of the embodiments, the practical application or technicalimprovement over technologies found in the marketplace, or to enableothers of ordinary skill in the art to understand the embodimentsdisclosed herein.

What is claimed is:
 1. A computer-implemented method comprising:executing one or more tests on a computing device, wherein the computingdevice comprises Instruction Execution Protection (IEP), and whereineach test of the one or more tests comprises selectively setting one ormore IEP bits of one or more page tables, wherein each IEP bit preventscode in a respective storage block from being executed; detecting, by acomputer processor of the computing device, during the one or moretests, an IEP exception each time an attempt is made to execute code ina storage block for which a respective IEP bit is set; determining testresults of the one or more tests based on the detecting; and performinga remedial action in response to the test results of the one or moretests.
 2. The computer-implemented method of claim 1, wherein executinga first test of the one or more tests comprises: instructing auniprocessor to execute code in one or more protected storage blockshaving respective IEP bits that are set; and instructing theuniprocessor to execute code in one or more unprotected storage blockshaving respective IEP bits that are not set; wherein the detecting theIEP exception each time an attempt is made to execute code in a storageblock for which a respective IEP bit is set comprises detecting an IEPexception each time the uniprocessor attempts to execute code in the oneor more protected storage blocks.
 3. The computer-implemented method ofclaim 1, wherein executing a first test of the one or more testscomprises: instructing a master processor of a multiprocessor system toset the one or more IEP bits of the one or more page tables, wherein theone or more page tables correspond to one or more protected storageblocks in a common storage shared with a first set of slave processors;wherein the detecting the IEP exception each time an attempt is made toexecute code in a storage block for which a respective IEP bit is setcomprises detecting an IEP exception each time at least one of themaster processor and the first set of slave processors attempts toexecute code in the one or more protected storage blocks in commonstorage.
 4. The computer-implemented method of claim 3, wherein theexecuting the first test of the one or more tests further comprises:instructing a second set of slave processors of the multiprocessorsystem to execute code in a second storage, wherein the second storageis absent protected storage blocks with respective IEP bits that areset.
 5. The computer-implemented method of claim 1, wherein executing afirst test of the one or more tests comprises: instructing a masterprocessor of a multiprocessor system to execute code in a first storage,wherein the first storage is absent protected storage blocks withrespective IEP bits that are set; instructing the master processor toset the one or more IEP bits of the one or more page tables, wherein theone or more page tables correspond to one or more protected storageblocks in a second storage; instructing a first set of slave processorsof the multiprocessor system to execute code in the second storage;wherein the detecting the IEP exception each time an attempt is made toexecute code in a storage block for which a respective IEP bit is setcomprises detecting an IEP exception each time at least one of the firstset of slave processors attempts to execute code in the one or moreprotected storage blocks in the second storage.
 6. Thecomputer-implemented method of claim 5, wherein the executing the firsttest of the one or more tests further comprises: instructing a secondset of slave processors of the multiprocessor system to execute code ina third storage, wherein the third storage is absent protected storageblocks with respective IEP bits that are set.
 7. Thecomputer-implemented method of claim 1, wherein executing a first testof the one or more tests comprises: instructing a master processor of amultiprocessor system to execute code in a first storage; instructingthe master processor to set the one or more IEP bits of the one or morepage tables, wherein the one or more page tables correspond to one ormore protected storage blocks in the first storage; instructing one ormore slave processors of the multiprocessor system to execute code inthe second storage, wherein the second storage is absent protectedstorage blocks with respective IEP bits that are set; wherein thedetecting the IEP exception each time an attempt is made to execute codein a storage block for which a respective IEP bit is set comprisesdetecting an IEP exception each time the master processor attempts toexecute code in the one or more protected storage blocks in the firststorage.
 8. The computer-implemented method of claim 1, wherein theremedial action comprises reporting the test results of the one or moretest programs.
 9. A system comprising: a memory having computer-readableinstructions; and one or more processors for executing thecomputer-readable instructions, the computer readable instructionscomprising: executing one or more tests on a computing device, whereinthe computing device comprises Instruction Execution Protection (IEP),and wherein each test of the one or more tests comprises selectivelysetting one or more IEP bits of one or more page tables, wherein eachIEP bit prevents code in a respective storage block from being executed;detecting, during the one or more tests, an IEP exception each time anattempt is made to execute code in a storage block for which arespective IEP bit is set; determining test results of the one or moretests based on the detecting; and performing a remedial action inresponse to the test results of the one or more tests.
 10. The system ofclaim 9, wherein executing a first test of the one or more testscomprises: instructing a uniprocessor to execute code in one or moreprotected storage blocks having respective IEP bits that are set; andinstructing the uniprocessor to execute code in one or more unprotectedstorage blocks having respective IEP bits that are not set; wherein thedetecting the IEP exception each time an attempt is made to execute codein a storage block for which a respective IEP bit is set comprisesdetecting an IEP exception each time the master processor attempts toexecute code in the one or more protected storage blocks.
 11. The systemof claim 9, wherein executing a first test of the one or more testscomprises: instructing a master processor of a multiprocessor system toset the one or more IEP bits of the one or more page tables, wherein theone or more page tables correspond to one or more protected storageblocks in a common storage shared with a first set of slave processors;wherein the detecting the IEP exception each time an attempt is made toexecute code in a storage block for which a respective IEP bit is setcomprises detecting an IEP exception each time at least one of themaster processor and the first set of slave processors attempts toexecute code in the one or more protected storage blocks in commonstorage.
 12. The system of claim 9, wherein executing a first test ofthe one or more tests comprises: instructing a master processor of amultiprocessor system to execute code in a first storage, wherein thefirst storage is absent protected storage blocks with respective IEPbits that are set; instructing the master processor to set the one ormore IEP bits of the one or more page tables, wherein the one or morepage tables correspond to one or more protected storage blocks in asecond storage; instructing a first set of slave processors of themultiprocessor system to execute code in the second storage; wherein thedetecting the IEP exception each time an attempt is made to execute codein a storage block for which a respective IEP bit is set comprisesdetecting an IEP exception each time at least one of the first set ofslave processors attempts to execute code in the one or more protectedstorage blocks in the second storage.
 13. The system of claim 9, whereinexecuting a first test of the one or more tests comprises: instructing amaster processor of a multiprocessor system to execute code in a firststorage; instructing the master processor to set the one or more IEPbits of the one or more page tables, wherein the one or more page tablescorrespond to one or more protected storage blocks in the first storage;instructing one or more slave processors of the multiprocessor system toexecute code in the second storage, wherein the second storage is absentprotected storage blocks with respective IEP bits that are set; whereinthe detecting the IEP exception each time an attempt is made to executecode in a storage block for which a respective IEP bit is set comprisesdetecting an IEP exception each time the master processor attempts toexecute code in the one or more protected storage blocks in the firststorage.
 14. The system of claim 9, wherein the remedial actioncomprises reporting the test results of the one or more test programs.15. A computer-program product for testing functionality of InstructionExecution Protection (IEP), the computer-program product comprising acomputer-readable storage medium having program instructions embodiedtherewith, the program instructions executable by a processor to causethe processor to perform a method comprising: executing one or moretests on a computing device, wherein the computing device comprises IEP,and wherein each test of the one or more tests comprises selectivelysetting one or more IEP bits of one or more page tables, wherein eachIEP bit prevents code in a respective storage block from being executed;detecting, during the one or more tests, an IEP exception each time anattempt is made to execute code in a storage block for which arespective IEP bit is set; determining test results of the one or moretests based on the detecting; and performing a remedial action inresponse to the test results of the one or more tests.
 16. Thecomputer-program product of claim 15, wherein executing a first test ofthe one or more tests comprises: instructing a uniprocessor to executecode in one or more protected storage blocks having respective IEP bitsthat are set; and instructing the uniprocessor to execute code in one ormore unprotected storage blocks having respective IEP bits that are notset; wherein the detecting the IEP exception each time an attempt ismade to execute code in a storage block for which a respective IEP bitis set comprises detecting an IEP exception each time the masterprocessor attempts to execute code in the one or more protected storageblocks.
 17. The computer-program product of claim 15, wherein executinga first test of the one or more tests comprises: instructing a masterprocessor of a multiprocessor system to set the one or more IEP bits ofthe one or more page tables, wherein the one or more page tablescorrespond to one or more protected storage blocks in a common storageshared with a first set of slave processors; wherein the detecting theIEP exception each time an attempt is made to execute code in a storageblock for which a respective IEP bit is set comprises detecting an IEPexception each time at least one of the master processor and the firstset of slave processors attempts to execute code in the one or moreprotected storage blocks in common storage.
 18. The computer-programproduct of claim 15, wherein executing a first test of the one or moretests comprises: instructing a master processor of a multiprocessorsystem to execute code in a first storage, wherein the first storage isabsent protected storage blocks with respective IEP bits that are set;instructing the master processor to set the one or more IEP bits of theone or more page tables, wherein the one or more page tables correspondto one or more protected storage blocks in a second storage; instructinga first set of slave processors of the multiprocessor system to executecode in the second storage; wherein the detecting the IEP exception eachtime an attempt is made to execute code in a storage block for which arespective IEP bit is set comprises detecting an IEP exception each timeat least one of the first set of slave processors attempts to executecode in the one or more protected storage blocks in the second storage.19. The computer-program product of claim 15, wherein executing a firsttest of the one or more tests comprises: instructing a master processorof a multiprocessor system to execute code in a first storage;instructing the master processor to set the one or more IEP bits of theone or more page tables, wherein the one or more page tables correspondto one or more protected storage blocks in the first storage;instructing one or more slave processors of the multiprocessor system toexecute code in the second storage, wherein the second storage is absentprotected storage blocks with respective IEP bits that are set; whereinthe detecting the IEP exception each time an attempt is made to executecode in a storage block for which a respective IEP bit is set comprisesdetecting an IEP exception each time the master processor attempts toexecute code in the one or more protected storage blocks in the firststorage.
 20. The computer-program product of claim 15, wherein theremedial action comprises reporting the test results of the one or moretest programs.